Site and Structural Requirements for the Dehydra-Decyclization of Cyclic Ethers on ZrO₂

In this study, we examined the site and structural requirements for the dehydra-decyclization of cyclic ethers, tetrahydrofuran, and tetrahydropyran to produce conjugated dienes over ZrO₂-based catalysts, a reaction that could be an important step in the use of biomass-derived sugars as a starting material to produce monomers for the plastics industry. To help identify the active sites for this reaction, studies were conducted in which ZrO₂ surfaces were decorated with Na. These studies showed that Na was effective at poisoning the activity for the ring opening of cyclic ethers, but much less so for the dehydration of the resulting adsorbed alkoxides. The studies of the activity of different types of ZrO₂ for the dehydra-decyclization reaction, including single crystals and ultra-thin films supported on MgAl₂O₄ and silica, also showed that the reaction was dependent on the local structure of the ZrO₂ surface. The insights these results provide for identifying the active sites on the ZrO₂ surface are discussed.